Racing lower unit

ABSTRACT

Disclosed herein is a marine propulsion device comprising a lower unit including exhaust gas discharge means located in the lower unit for discharging gas, during forward travel, into the area in front of the upper half of the path of the blades of a propeller rotatably carried by the lower unit.

1451 July 17, 1973 United States Patent 11 1 Henrich RACING LOWER UNIT [54] 1,931,075 10/1933 .lohns0n............ 3,350,879 11/1967 Boda ct 1751 lnvenm m Lake 3,431,882 3/1969 lrgens Assignee: Outboard Marine Corporation,

Waukegan, [11.

Aug. 19, 1971 Primary Examiner-Milton Buchler Assistant Examiner-Carl A. Rutledge Att0rneyRobcrt E. Clemency et a].

[22] Filed:

[21] Appl. No.: 173,065

ABSTRACT I [52] US. 115/34 R, 115/17, 115/.5 [51] Int. B63h 19/06 Dlsclosed harem a manna PTOIPUISIO devce 5/34, 35 17, 18, prising a lower unit including exhaust gas discharge means located in the lower unit for discharging gas, during forward travel, into the area in front of the [58] Field of Search upper half of the path of the blades of a propeller rotatably carried by the lower unit.

References Cited UNITED STATES PATENTS 1,073,920 Miller 115/17 10 Claims, 2 Drawing Figures RACING LOWER UNIT BACKGROUND OF THE INVENTION The invention relates generally to marine propulsion devices. More particularly, the invention relates to marine propulsion lower units which drive racing propellers and which are adapted for racing. Still more particularly, the invention relates to arrangements for discharging exhaust gases from marine propulsion lower units.

Racing propellers are commonly designed to operate at least partially out of the water so as to facilitate operation at relatively high rotational speeds and so as to provide lift to the stern of the supporting boat hull. Whenever the boat is traveling at a relatively slow speed, as for instance, during starting or turning, there is a tendency for the stern of the boat to settle in the water and thereby to more or less submerge the propeller completely in the water. Such submergence tends to disadvantageously reduce the rotational speed of the propeller. Such reduction in rotational speed is believed to occur when the propeller is more or less fully submerged because the propeller is then rotating in more or less solid water.

Some examples of prior exhaust gas discharge arrangements for marine propulsion lower units are disclosed in the U.S. Pat. Nos. 3,537,419 issued Aug. 18, 1969, No. 3,467,051 issued Sept. 16, 1969, No. 2,609,782 issued Sept. 9, 1952, and No. 3,046,903 issued July 13, 1962, as well as in Canadian Pat. No. 687,868 issued June 21, 1964 and No. 631,169 issued Nov. 12,1961.

SUMMARY OF THE INVENTION The invention is directed to reducing the solidity of the water in the area above the propeller shaft or in the upper half of the path of the propeller blades by introducing from the lower unit, a gas, such as air or exhaust gas into the area in the front of the top half of the path of the propeller blades.

The invention provides a marine propulsion lower unit including means operating during forward travel for discharging exhaust or other gas from the lower unit forwardly of the propeller blades and into the area above the propeller shaft and adjacent to the top half of the path of the propeller blades. As a result, the density of the water in the area abovethe propeller shaft, and through which the propeller blades travel, is re- In accordance with the invention, exhaust gases or air can be introduced. Preferably, exhaust gas is discharged through a series of vertically spaced ports located in a transversely flat aft margin of the lower unit above the propeller shaft and below the cavitation plate.

During forward travel when the propeller is only partially submerged, the gases exiting from the ports are discharged to the atmosphere. when the propeller is more or less fully submerged, the gas discharged through the ports reduces the solidity" of the water and permits faster propeller rotation.

One of the principal objects of the invention is the provision of a racing marine propulsion lower unit including means for discharging gases forwardly of the upper half of the path of the propeller blades so that, when the propeller is more or less fully submerged, the

water in the upper half of the pathof the propeller blades is desolidified.

Another of the principal objects of the invention is,

the provision of a racing lower unit which is capable of providing superior forward thrust for a given engine output and therefor capable of driving a boat at a faster speed for a given engine operating condition.

Another of the principal objects of the invention is the provision of a racing lower unit arrangement which provides more effective forward thrust and which can be readily obtained by modifying a conventional lower unit.

Other objects and advantages of the invention will become known by reference to the following description and accompanying drawings.

DRAWINGS FIG. 1 is a perspective view, partially broken away and in section, of a marine propulsion lower unit including various of the features of the invention.

FIG. 2 is a fragmentary view, in section, taken along line 22 of FIG. 1.

Before explaining the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

DETAILED DESCRIPTION Shown in the drawings is a marine propulsion lower unit 11 which embodies various of the features of the invention and which can be a part of either an outboard motor or a stern drive unit. The lower unit 11 includes a drive shaft housing portion 13 which, at its lower end, is joined to a gearcase portion 17.

Extending through the device shaft housing portion 13 is a drive shaft 19 which is powered by an engine (not shown) and which extends into the gearcase portion 17 and is connected by suitable gearing 21 with a propeller shaft 23 carrying a racing propeller 27. While various propellers can be employed,'the illustrated propeller 27 includes two blades 29. Single bladed propellers and propellers with more than two blades can also be employed. i

The gearcase portion 17 is also formed with a cavitation plate 31 which is located slightly above the top of the path of the propeller blades 29.

Also provided in the lower unit is an exhaust gas passage system. In this regard, the gearcase portion 17 is formed with an exhaust gas passage or conduit 33 which communicates with the hollow interior of the drive shaft housing portion or other suitable exhaust gas passageway 37in the drive shaft housing portion 13 and which includes an exhaust gas discharge outlet 39 rearwardly of the path of rotation of the propeller blades 29. The discharge outlet 39 can be either above or below the cavitation plate 31. As thus far described, the lower unit 11 is generally conventionally constructed.

In accordance with the invention, there is provided means for discharging gases and, in the particularly disclosed embodiment, exhaust gases, from the lower unit 1 l forwardlyof the path of the propeller blades 29 and generally into the upper half of the path of the propeller blades 29. While other constructions can be employed, in the disclosed construction, there is provided in the gearcase portion 17 of the lower unit 11 a bore 41 which extends vertically downwardly from the exhaust gas conduit 33 and which communicates with a series of vertically spaced fore and aft bores 43 which terminate in ports 47 located in a transversely flat rearward trailing edge 49.

In one particular embodiment, the trailing edge 49 has a width of about 56 inch and there are seven vertically spaced bores 43, each with a diameter of about /32 inch and each communicating with the generally vertical bore 41 which has a diameter of about inch. The disclosed ports 47 of the vertically spaced bores 43 are evenly spaced at distances of about '75 inch from centerline to centerline and thus extended over a vertical range of about 3% inch.

The discharge ports 47 are all located below the cavitation plate 31 and above a boss 51 formed on the gearcase portion 17 around the propeller shaft 23. It is believed that at least some of the advantages of the invention can be obtained when using a discharge configuration which is located, at least in part, as high as about 2 inches above the path of the propeller blades 29.

In operation, a portion of the exhaust gas exits through the discharge outlet 39 rearwardly of the propeller 27 and, when the propeller 27 is operating partially out of the water, another portion of the exhaust gases is discharged through the ports 47 to the atmosphere. When the propeller 27 is more or less fully submerged in water, a portion of the exhaust gas exits from the ports 47 and serves to desolidify the water in the area of the upper half of the path of the propeller blades 29 and in front of the propeller 27. The transverse flat or edge 49 serves to assists in aspirating exhaust gas out through the discharge ports 47 as the transverse flat 49 produces a trailing void during passage of the lower unit 11 through the water. Introduction of gases into the void also serves to reduce the drag on forward movement of the lower unit through the water. The area behind the flat 49 is also ventilated, when the cavitation plate 31 is above water by travel of atmoshperic air into the void behind the flat 47.

Various of the features of the invention are set forth in the following claims.

I claim:

l. A marine propulsion device comprising a lower unit including a propeller shaft, means rotatably supporting said propeller shaft on said lower unit, a transversely flat rearward surface at the rear of said lower unit above said propeller shaft, a propeller mounted on said shaft rearwardly of said flat surface and for com- .mon rotation with said shaft and having at least one propeller blade, and a bore terminating in a port in said flat surface at the rear of said lower unit and communieating with a source of gas to provide for discharge of gas, during forward travel, into the area in front of the upper half of the path of said propeller blade.

2. A marine propulsion device in accordance with claim 1 and including a plurality of said bores in vertically spaced relation.

3. A marine propulsion device in'aecordance with claim 1 wherein said lower unit includes an exhaust gas passage system and said bore communicates with said system.

4. A marine propulsion device in accordance with claim 1 wherein said lower unit includes a cavitation plate and said transversely flat rearward surface is located below said cavitation plate.

5. A marine propulsion device including a lower unit including an exhaust gas passage system, a cavitation plate, and a transversely flat rearward surface below said cavitation plate, a propeller shaft, means rotatably supporting said propeller shaft in said lower unit below said surface, a propeller mounted on said shaft rearwardly of said surface and for common rotation with said shaft and having at least one propeller blade and a plurality of vertically spaced bores respectively terminating in ports at said surface and communicating with said exhaust gas passage system.

6. A marine propulsion device comprising a lower unit including a cavitation plate, a propeller shaft, means rotatably supporting said propeller shaft on said lower unit below said cavitation plate, a propeller mounted on said shaft for common rotation therewith and having at least one propeller blade, and a bore extending in said lower unit, communicating with a source of gas and terminating in a port located at the rear of said lower unit in front of said propeller and below said cavitation plate and above said propeller shaft.

7. A marine propulsion device in accordance with claim 6 including a plurality of said bores located in vertically spaced relation between said cavitation plate and said propeller shaft at the rear of said lower unit.

8. A marine propulsion device in accordance with claim 7 wherein said lower unit includes an exhaust gas passage system and said bores communicate with said system.

9. A marine propulsion device comprising a lower unit including a propeller shaft, means rotatably supporting said propeller shaft on said lower unit, a propeller'mounted on said shaft for common rotation therewith and having at least one propeller blade, and a plurality of bores extending in said lower unit and communicating with a source of gas and terminating in vertically spaced ports located at the rear of said lower unit and in front of the upper half of the path of said propeller blade.

10. A marine propulsion device in accordance with claim 9 wherein said lower unit includes an exhaust gas passage system and said bores communicate with said system. 

1. A marine propulsion device comprising a lower unit including a propeller shaft, means rotatably supporting said propeller shaft on said lower unit, a transversely flat rearward surface at the rear of said lower unit above said propeller shaft, a propeller mounted on said shaft rearwardly of said flat surface and for common rotation with said shaft and having at least one propeller blade, and a bore terminating in a port in said flat surface at the rear of said lower unit and communicating with a source of gas to provide for discharge of gas, during forward travel, into the area in front of the upper half of the path of said propeller blade.
 2. A marine propulsion device in accordance with claim 1 and including a plurality of said bores in vertically spaced relation.
 3. A marine propulsion device in accordance with claim 1 wherein said lower unit includes an exhaust gas passage system and said bore communicates with said system.
 4. A marine propulsion device in accordance with claim 1 wherein said lower unit includes a cavitation plate and said transversely flat rearward surface is located below said cavitation plate.
 5. A marine propulsion device including a lower unit including an exhaust gas passage system, a cavitation plate, and a transversely flat rearward surface below said cavitation plate, a propeller shaft, means rotatably supporting said propeller shaft in said lower unit below said surface, a propeller mounted on said shaft rearwardly of said surface and for common rotation with said shaft and having at least one propeller blade and a plurality of vertically spaced bores respectively terminating in ports at said surface and communicating with said exhaust gas passage system.
 6. A marine propulsion device comprising a lower unit including a cavitation plate, a propeller shaft, means rotatably supporting said propeller shaft on said lower unit below said cavitation plate, a propeller mounted on said shaft for common rotation therewith and having at least one propeller blade, and a bore extending in said lower unit, communicating with a source of gas and terminating in a port located at the rear of said lower unit in front of said propeller and below said cavitation plate and above said propeller shaft.
 7. A marine propulsioN device in accordance with claim 6 including a plurality of said bores located in vertically spaced relation between said cavitation plate and said propeller shaft at the rear of said lower unit.
 8. A marine propulsion device in accordance with claim 7 wherein said lower unit includes an exhaust gas passage system and said bores communicate with said system.
 9. A marine propulsion device comprising a lower unit including a propeller shaft, means rotatably supporting said propeller shaft on said lower unit, a propeller mounted on said shaft for common rotation therewith and having at least one propeller blade, and a plurality of bores extending in said lower unit and communicating with a source of gas and terminating in vertically spaced ports located at the rear of said lower unit and in front of the upper half of the path of said propeller blade.
 10. A marine propulsion device in accordance with claim 9 wherein said lower unit includes an exhaust gas passage system and said bores communicate with said system. 